Abstract Background Polysomnography (PSG) is the gold standard for diagnosing obstructive sleep apnea (OSA). However, it is time-consuming, expensive and requires technical expertise. Thus, a number of alternatives to PSG have been proposed. The present study was conducted to analyse the sensitivity, specificity and accuracy of night oximetry as a diagnostic tool in patients suspected to have ... [Show full abstract] sleep apnea hypopnea syndrome (SAHS), and to reduce the number of saved PSGs. Patients and methods In total, 40 middle-aged patients clinically suspected to haveObstructive Sleep Apnea Hypopnea Syndrome (OSAHS) were included in the study. They were classified into two groups: group I (the SAHS group), comprising 33patientswithapneahypopneaindex greater than or equal to5; and group II (the non-SAHS group), comprising seven patients with apnea hypopnea index l than 5. All patients were subjected to the following: (a) OSA screening questionnaire; (b) BMI in kg/m2, neck circumference in cm, and cardiac, chest and ENT examinations; (c) investigationintheform of arterialbloodgases, chest radiograph, ECG and spirometry; and (d) full PSG and overnight oximetry, which were carried out simultaneously. Results The baseline values of O2 saturation derived from PSG and oximetry were 93.33±2.32 and 91.50±2.79, respectively. The overnight oxygen desaturation index of oximetry was significantly lower in the SAHS group. Minimal SpO2 of PSG was significantly lower in the SAHS group. The best predicted cutoff value of overnight pulse oximetry using oxygen desaturation index for mild to moderate OSA patient diagnosis was 14.78, with 87.88% sensitivity and 88.71% specificity. However, the optimal cutoff value for severe OSA diagnosis was 52.55, with 86.67% sensitivity and 96% specificity. Conclusion Overnight pulse oximetry may be considered a diagnostic tool in patients suspected to have SAHS, with excellent diagnostic sensitivity, specificity and accuracy, which increased with severity.